I doubt you’ll be adding this to your home recording studio rig anytime soon, but it’s still cool nonetheless. This microphone was made out of a piezo pickup, 1/8th-inch jack, and a tin can. I never thought about it, but yes, I suppose this is about the simplest microphone one could ever build. No clue on how the quality of the mic is, but it looks like it could give off a real vintage sound.
Tin Can Mic [MAKE]